The flow and volume values measured under these
conditions are marked with BTPS*. On the other hand,
medical gases from cylinders or from the central supply
are dry (approx. 0 % r.h.) and are delivered by the
ventilator at 20 °C. The flow and volume values
measured under these conditions are marked NTPD**.
The difference between measured values under NTPD
and BTPS conditions is typically approx. 12 %.
Example: a tidal volume of 500 mL NTPD is increased to
564 mL BTPS by heating to 37 °C and humidifying to
100 % r.h..
Evita 4 delivers the tidal volume after conversion, so that
the set tidal volume is effective in the lung under BTPS
conditions.
____________
* BTPS = Body Temperature, Pressure, Saturated.
** NTPD = Normal Temperature Pressure Dry.
171
Description
Ventilation Modes
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